Improve automatic mirror switching

app/src/main/kotlin/org/koitharu/kotatsu/core/network/MirrorSwitchInterceptor.kt

@@ -1,6 +1,9 @@
 package org.koitharu.kotatsu.core.network
 
+import androidx.collection.ArraySet
 import dagger.Lazy
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runInterruptible
 import okhttp3.Interceptor
 import okhttp3.Request
 import okhttp3.Response
@@ -13,6 +16,7 @@ import org.koitharu.kotatsu.core.parser.MangaRepository
 import org.koitharu.kotatsu.core.parser.RemoteMangaRepository
 import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.parsers.model.MangaSource
+import java.util.EnumMap
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -22,9 +26,15 @@ class MirrorSwitchInterceptor @Inject constructor(
 	private val settings: AppSettings,
 ) : Interceptor {
 
+	private val locks = EnumMap<MangaSource, Any>(MangaSource::class.java)
+	private val blacklist = EnumMap<MangaSource, MutableSet<String>>(MangaSource::class.java)
+
+	val isEnabled: Boolean
+		get() = settings.isMirrorSwitchingAvailable
+
 	override fun intercept(chain: Interceptor.Chain): Response {
 		val request = chain.request()
-		if (!settings.isMirrorSwitchingAvailable) {
+		if (!isEnabled) {
 			return chain.proceed(request)
 		}
 		return try {
@@ -43,6 +53,30 @@ class MirrorSwitchInterceptor @Inject constructor(
 		}
 	}
 
+	suspend fun trySwitchMirror(repository: RemoteMangaRepository): Boolean = runInterruptible(Dispatchers.Default) {
+		if (!isEnabled) {
+			return@runInterruptible false
+		}
+		val mirrors = repository.getAvailableMirrors()
+		if (mirrors.size <= 1) {
+			return@runInterruptible false
+		}
+		synchronized(obtainLock(repository.source)) {
+			val currentMirror = repository.domain
+			addToBlacklist(repository.source, currentMirror)
+			val newMirror = mirrors.firstOrNull { x ->
+				x != currentMirror && !isBlacklisted(repository.source, x)
+			} ?: return@synchronized false
+			repository.domain = newMirror
+			true
+		}
+	}
+
+	fun rollback(repository: RemoteMangaRepository, oldMirror: String) = synchronized(obtainLock(repository.source)) {
+		blacklist[repository.source]?.remove(oldMirror)
+		repository.domain = oldMirror
+	}
+
 	private fun trySwitchMirror(request: Request, chain: Interceptor.Chain): Response? {
 		val source = request.tag(MangaSource::class.java) ?: return null
 		val repository = mangaRepositoryFactoryLazy.get().create(source) as? RemoteMangaRepository ?: return null
@@ -50,7 +84,9 @@ class MirrorSwitchInterceptor @Inject constructor(
 		if (mirrors.isEmpty()) {
 			return null
 		}
-		return tryMirrors(repository, mirrors, chain, request)
+		return synchronized(obtainLock(repository.source)) {
+			tryMirrors(repository, mirrors, chain, request)
+		}
 	}
 
 	private fun tryMirrors(
@@ -66,7 +102,7 @@ class MirrorSwitchInterceptor @Inject constructor(
 		}
 		val urlBuilder = url.newBuilder()
 		for (mirror in mirrors) {
-			if (mirror == currentDomain) {
+			if (mirror == currentDomain || isBlacklisted(repository.source, mirror)) {
 				continue
 			}
 			val newHost = hostOf(url.host, mirror) ?: continue
@@ -75,6 +111,7 @@ class MirrorSwitchInterceptor @Inject constructor(
 				.build()
 			val response = chain.proceed(newRequest)
 			if (response.isFailed) {
+				addToBlacklist(repository.source, mirror)
 				response.closeQuietly()
 			} else {
 				repository.domain = mirror
@@ -104,4 +141,18 @@ class MirrorSwitchInterceptor @Inject constructor(
 	private fun ResponseBody.copy(): ResponseBody {
 		return source().readByteArray().toResponseBody(contentType())
 	}
+
+	private fun obtainLock(source: MangaSource): Any = locks.getOrPut(source) {
+		Any()
+	}
+
+	private fun isBlacklisted(source: MangaSource, domain: String): Boolean {
+		return blacklist[source]?.contains(domain) == true
+	}
+
+	private fun addToBlacklist(source: MangaSource, domain: String) {
+		blacklist.getOrPut(source) {
+			ArraySet(2)
+		}.add(domain)
+	}
 }

app/src/main/kotlin/org/koitharu/kotatsu/core/parser/MangaRepository.kt

@@ -2,6 +2,7 @@ package org.koitharu.kotatsu.core.parser
 
 import androidx.annotation.AnyThread
 import org.koitharu.kotatsu.core.cache.ContentCache
+import org.koitharu.kotatsu.core.network.MirrorSwitchInterceptor
 import org.koitharu.kotatsu.local.data.LocalMangaRepository
 import org.koitharu.kotatsu.parsers.MangaLoaderContext
 import org.koitharu.kotatsu.parsers.model.Manga
@@ -43,6 +44,7 @@ interface MangaRepository {
 		private val localMangaRepository: LocalMangaRepository,
 		private val loaderContext: MangaLoaderContext,
 		private val contentCache: ContentCache,
+		private val mirrorSwitchInterceptor: MirrorSwitchInterceptor,
 	) {
 
 		private val cache = EnumMap<MangaSource, WeakReference<RemoteMangaRepository>>(MangaSource::class.java)
@@ -55,7 +57,11 @@ interface MangaRepository {
 			cache[source]?.get()?.let { return it }
 			return synchronized(cache) {
 				cache[source]?.get()?.let { return it }
-				val repository = RemoteMangaRepository(MangaParser(source, loaderContext), contentCache)
+				val repository = RemoteMangaRepository(
+					parser = MangaParser(source, loaderContext),
+					cache = contentCache,
+					mirrorSwitchInterceptor = mirrorSwitchInterceptor,
+				)
 				cache[source] = WeakReference(repository)
 				repository
 			}

app/src/main/kotlin/org/koitharu/kotatsu/core/parser/RemoteMangaRepository.kt

@@ -13,11 +13,13 @@ import okhttp3.Response
 import org.koitharu.kotatsu.BuildConfig
 import org.koitharu.kotatsu.core.cache.ContentCache
 import org.koitharu.kotatsu.core.cache.SafeDeferred
+import org.koitharu.kotatsu.core.network.MirrorSwitchInterceptor
 import org.koitharu.kotatsu.core.prefs.SourceSettings
 import org.koitharu.kotatsu.core.util.ext.processLifecycleScope
 import org.koitharu.kotatsu.parsers.MangaParser
 import org.koitharu.kotatsu.parsers.MangaParserAuthProvider
 import org.koitharu.kotatsu.parsers.config.ConfigKey
+import org.koitharu.kotatsu.parsers.exception.ParseException
 import org.koitharu.kotatsu.parsers.model.Favicons
 import org.koitharu.kotatsu.parsers.model.Manga
 import org.koitharu.kotatsu.parsers.model.MangaChapter
@@ -31,6 +33,7 @@ import org.koitharu.kotatsu.parsers.util.runCatchingCancellable
 class RemoteMangaRepository(
 	private val parser: MangaParser,
 	private val cache: ContentCache,
+	private val mirrorSwitchInterceptor: MirrorSwitchInterceptor,
 ) : MangaRepository, Interceptor {
 
 	override val source: MangaSource
@@ -66,11 +69,15 @@ class RemoteMangaRepository(
 	}
 
 	override suspend fun getList(offset: Int, query: String): List<Manga> {
-		return parser.getList(offset, query)
+		return mirrorSwitchInterceptor.withMirrorSwitching {
+			parser.getList(offset, query)
+		}
 	}
 
 	override suspend fun getList(offset: Int, tags: Set<MangaTag>?, sortOrder: SortOrder?): List<Manga> {
-		return parser.getList(offset, tags, sortOrder)
+		return mirrorSwitchInterceptor.withMirrorSwitching {
+			parser.getList(offset, tags, sortOrder)
+		}
 	}
 
 	override suspend fun getDetails(manga: Manga): Manga = getDetails(manga, withCache = true)
@@ -78,17 +85,25 @@ class RemoteMangaRepository(
 	override suspend fun getPages(chapter: MangaChapter): List<MangaPage> {
 		cache.getPages(source, chapter.url)?.let { return it }
 		val pages = asyncSafe {
-			parser.getPages(chapter).distinctById()
+			mirrorSwitchInterceptor.withMirrorSwitching {
+				parser.getPages(chapter).distinctById()
+			}
 		}
 		cache.putPages(source, chapter.url, pages)
 		return pages.await()
 	}
 
-	override suspend fun getPageUrl(page: MangaPage): String = parser.getPageUrl(page)
+	override suspend fun getPageUrl(page: MangaPage): String = mirrorSwitchInterceptor.withMirrorSwitching {
+		parser.getPageUrl(page)
+	}
 
-	override suspend fun getTags(): Set<MangaTag> = parser.getTags()
+	override suspend fun getTags(): Set<MangaTag> = mirrorSwitchInterceptor.withMirrorSwitching {
+		parser.getTags()
+	}
 
-	suspend fun getFavicons(): Favicons = parser.getFavicons()
+	suspend fun getFavicons(): Favicons = mirrorSwitchInterceptor.withMirrorSwitching {
+		parser.getFavicons()
+	}
 
 	override suspend fun getRelated(seed: Manga): List<Manga> {
 		cache.getRelatedManga(source, seed.url)?.let { return it }
@@ -105,7 +120,9 @@ class RemoteMangaRepository(
 		}
 		cache.getDetails(source, manga.url)?.let { return it }
 		val details = asyncSafe {
-			parser.getDetails(manga)
+			mirrorSwitchInterceptor.withMirrorSwitching {
+				parser.getDetails(manga)
+			}
 		}
 		cache.putDetails(source, manga.url, details)
 		return details.await()
@@ -155,4 +172,33 @@ class RemoteMangaRepository(
 		}
 		return result
 	}
+
+	private suspend fun <R> MirrorSwitchInterceptor.withMirrorSwitching(block: suspend () -> R): R {
+		if (!isEnabled) {
+			return block()
+		}
+		val initialMirror = domain
+		val result = runCatchingCancellable {
+			block()
+		}
+		if (result.isValidResult()) {
+			return result.getOrThrow()
+		}
+		return if (trySwitchMirror(this@RemoteMangaRepository)) {
+			val newResult = runCatchingCancellable {
+				block()
+			}
+			if (newResult.isValidResult()) {
+				return newResult.getOrThrow()
+			} else {
+				rollback(this@RemoteMangaRepository, initialMirror)
+				return result.getOrThrow()
+			}
+		} else {
+			result.getOrThrow()
+		}
+	}
+
+	private fun Result<*>.isValidResult() = exceptionOrNull() !is ParseException
+		&& (getOrNull() as? Collection<*>)?.isEmpty() != true
 }